1. Field of the Invention
The present invention relates to an antenna beam scan module in an antenna device that combines and distributes phases using a Rotman lens.
2. Description of the Related Art
A phased array antenna has been known as a technique of selectively transmitting and receiving electromagnetic waves in a specific direction by scanning a beam. The phased array antenna composed of plural antenna elements can scan a beam by actively changing an electromagnetic phase plane from each antenna element. As a method of realizing the same, a variable phase shifter is provided for each antenna element to be independently controlled so that a desired beam angle is formed. Further, a phased array antenna without variable phase shifters can be realized by connection to each antenna element through a Rotman lens that can combine and distribute electromagnetic waves.
Japanese Patent Application Laid-Open Publication No. 2003-152422 is a related art of the technical field. This document describes “adder circuits are provided to add outputs from two beam ports 20-m and 20-(m+1) of a Rotman lens. A directivity angle between those of beams corresponding to two beam ports can be obtained by addition. Accordingly, the directivity angles of discrete beams can be interpolated” (see Abstract).
Further, Japanese Patent Application Laid-Open Publication No. 2010-074781 describes “a variable amplifier is provided at each of beam ports (transmission ports) BP1 and BP2 of a Rotman lens that forms a transmission beam and each of beam ports (reception ports) BP1 and BP2 of a Rotman lens that forms a reception beam to adjust the gain, so that the directivity of the transmission beam or the reception beam is adjusted. Accordingly, the transmission beam or the reception beam that is directed to an arbitrary direction other than a specified direction corresponding to each beam port can be realized with a simple configuration without using high-frequency switches” (see Abstract).
Further, Japanese Patent Application Laid-Open Publication No. 2006-287501 describes “the invention includes a coupler that extracts a transmission signal supplied to an antenna element through an RF circuit, a DFT (Discrete Fourier Transform) that converts the extracted signal to a signal of a frequency domain, an IDFT (Inverse Discrete Fourier Transform) that converts a signal output from a multiplier into a signal of a time domain, a delay unit that adds a delay temporally combined to the signal extracted through the RF circuit to a signal output from the IDFT, a DFT that converts the signal with the delay added into a signal of a frequency domain, a level/phase detector that detects a magnitude difference and a phase difference by comparing output signals from plural DFTs, a level/phase controller that offsets the magnitude and phase of a transmission signal of each antenna element in accordance with the detected result, and a multiplier” (see Abstract).